In fish, amphibians, and reptiles, the pineal gland has photosensitive cells - there are photochemical reactions needed to activate it. It also has brain connections that allow simple light-dark reactions, but it's not an eye.

In birds and mammals, the pineal gland winds up under the brain, and the photo activation is indirect, by way of the retinas.

Well, they say that this "third eye" thing is actually present in all of us, but not all becomes activated because we may choose it to be like it has never used to be. Paranormal things are associated with this third eye, and if you would wish not to see the unseen world, you might not want to exercise your mind with it, or else they say, your third eye would be activated and you will start feeling haunted.

---Just one act of random kindness at a time and you can change the world---